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the sinner
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Discussion Starter · #1 ·
A simple little trick that will work on just about any engine, costs very little money, and is just short of guaranteed to increase both torque and horsepower?

One of the most critical areas in a cylinder head is the transition from the port to the valve and into the cylinder. This is why multi-angle valve jobs have evolved-the search for improved flow. One simple trick that anyone can do is to add a 30-degree back cut to the inside diameter of the 45-degree seat angle on an intake and/or exhaust valve as a way to improve flow.

Question is how does this go with the SR engines, some engines have proven to be not so responsive to this method, I've done it with my VE head on N1 cams which broke after a few runs.

Does anyone here have a data or facts that this improves flow hence adding more torque and horsepower on an SR engine, VE VET and DET's?
 

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CAR SLÜT
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It really depends on the valve in question. The DET exhaust valves love multiangle seats due to their thicker sodium filled stem having a larger surface area behind the valve.

More importantly though, its matching air flow to the camshafts and the individual requirements of the engine. No point getting 500Hp worth of [email protected]"Hg if your oly aiming for 250Hp :)
 

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the sinner
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236 Posts
Discussion Starter · #3 ·
It really depends on the valve in question. The DET exhaust valves love multiangle seats due to their thicker sodium filled stem having a larger surface area behind the valve.

More importantly though, its matching air flow to the camshafts and the individual requirements of the engine. No point getting 500Hp worth of [email protected]"Hg if your oly aiming for 250Hp :)

how would the stock 20V valves handle this kind of mod? say lookin for 500hp from a boosted 20v + gt30 and N1 cams. get new valves perhaps and angle it or the surplus will do fine with the machine works? new guides on top of it, then gut to provision for the N1 cams?
 

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REV it up!!!!!
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You are looking for efficient power. Making more power at less boost. With a 20v head I would only do minimal port work but valve work is always good , 5 angle valve job in 15 deg increments 0r even 7-8 deg then adding a radius on the ex side. Raising the roof and widening the floor whilst make a good transition in to the bowl does wonders also. Making the guide short and tapering also increases flow. .look me up on the other side and you will see some good flow graphs of a worked sr20ve head...more than 350 cfms at .550-550" lift on intake and 250 on exhaust...the flow is very progressive. Head was to able the motor to do 550whp at 16-18lbs of boost conservative.
 

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REV it up!!!!!
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also the stock 20v valves will be okay or any stock valve/seat will do good with a valve job. The 20v head itself has better cooling than a regular sr head so if heat is your concern it should be okay.
 

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the sinner
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Discussion Starter · #6 ·
also the stock 20v valves will be okay or any stock valve/seat will do good with a valve job. The 20v head itself has better cooling than a regular sr head so if heat is your concern it should be okay.

Thanks daxx, being cautious right now since I'm thinking the first VE head had maybe heat issues and broke after doing 5 angle and gutting the guides. It was just stupid of me not to check when white smoke is already present

BTW are you watching MP in vegas?
 

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REV it up!!!!!
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Thanks daxx, being cautious right now since I'm thinking the first VE head had maybe heat issues and broke after doing 5 angle and gutting the guides. It was just stupid of me not to check when white smoke is already present

BTW are you watching MP in vegas?


I wish bro, I work so no MP for me but will watch on pay-per-view.


did you make the guides flush? If so it loses its rigidity and lets the valve(stem) get loose. also if you had heat issues it could be a plethora of things. Managing heat if your turbo'd is something that we tend to over look at times, more air you consume and burn the more heat the head will have to endure and expelling efficiently is needed so you dont have over heating issues.
 

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CAR SLÜT
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As far as coolant goes in the head, the VQ35HR engines actually redesigned the headgaskets so that water flows through the exhaust side of the head to cool the exhaust valves first rather than straight onto the intake valves like the original VQ35DE. The HR gaskets are also backwards compatible which is a pretty good idea. Would be interesting to see if blocking up or restricting the SR water galleries on the intake side of the block would allow more cold water onto the exhaust valves first and allow for a cooler valve...

The 20V head does as above have a better coolant design with more water flowing around the valves and spark plug to remove hot spots.
 

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the sinner
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Discussion Starter · #9 ·
My Ve head from the looks of it the exhaust valves gave out first, played jumping jacks in the 3rd chamber and broke the remaining three causing hell to brake loose.

I found a piece of the stem in the T3 which killed it. and yes the guides were flushed. 20v sounds to be a better option this time so I'll stick with it, and use the p11 Ve's solenoids.
 
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